1. Field of the Invention
The present invention relates to a damping force generating mechanism for generating a damping force by pressing an elastic body.
2. Description of the Background Art
A damping force generating mechanism is used for various portions required for absorbing vibration, for example, used for a so-called bottom link type suspension of a motorcycle in which a front wheel is suspended from lower end portions of a front fork through links. A general example of such a bottom link type suspension is shown in FIG. 16 (see Japanese Patent Laid-open No. Sho 62-187608).
Referring to FIG. 16, there is shown a scooter type motorcycle 01. A steering shaft 03 is turnably fitted in a head pipe 02. A pair of right and left front forked portions 04 are integrally mounted on the lower end of the steering shaft 03. A front wheel 06 is suspended from the lower ends of the front forked portions 04 through rocking arms 05 as link members.
With respect to the rocking arm 05, the base end thereof is pivotably supported on the lower end portion of the front forked portion 04, and the free end portion thereof rotatably supports the front wheel 06. A suspension spring 07 is interposed between the upper portion of the front forked portion 04 and an approximately central portion of the rocking arm 05.
A shock load applied to the front wheel from irregularities on the ground is damped by the suspension springs 07. However, when a shock load is applied with an abrupt shock load, the suspension springs are largely rebounded after being contracted once.
In an example described in Japanese Patent Publication No. Sho 57-49432, as shown in FIG. 17, a front end of a link 012 is pivotably supported on the lower end portion of a front forked portion 011 containing a hydraulic damping mechanism. A front wheel 013 is rotatably supported on a central portion of the link 012. A subcushion unit 14 is interposed between the rear end of the link 012 and the central portion of the front forked portion 011.
The subcushion unit 014 includes a cylindrical main body 015 pivotably mounted on the front forked portion 011. A piston 016 is slidably inserted in the cylindrical main body 015 and is connected to a leading end of a rod 017 pivotably mounted on the link 012. A cushion rubber 018 utilized as a damping member is inserted in the cylindrical main body 015 in such a manner as to be mounted on the upper surface of the piston 016. A stopper rubber 019 utilized as a stopper member is inserted in the cylindrical main body 015 in such a manner as to be mounted on the lower surface of the piston 016.
The subcushion unit 014 thus generates a compression side damping force by the cushion rubber 018, and also generates a tensile side damping force by the stopper rubber 019. Consequently, the subcushion unit 014 can suppress both the bound and rebound of the front wheel 013.
The above subcushion unit 014, however, has a disadvantage. Since the piston 016 is slid in the cylindrical main body 015, and the cushion rubber 018 and the stopper rubber 019 are separately provided on the upper and lower surfaces of the piston 016, the mechanism is complicated in structure, being heavy and expensive.